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Understanding Diamond Fluorescence

Diamond fluorescence is a fascinating and captivating property where a unique light is emitted when the precious gemstone is exposed to ultraviolet (UV) light. The diamond emits a light, colored glow. Usually, the glow is in blue color but can differ depending on the quality, appearance, and value of the precious diamond.

If you’re shopping for a diamond, understanding fluorescence in diamonds is crucial in ensuring you’re getting real, authentic, and quality gemstones. In this article, we’ll talk about what fluorescence in diamonds means and how it affects the quality and value of diamonds.

What is Diamond Fluorescence?

Diamond fluorescence is a natural occurrence where the diamond emits a lovely, visible glow. This typically happens when it is exposed to natural sunlight, lighting, or ultraviolet light. Then, the diamond will have this bluish light. But the color of the glow can have other colors such as orange, red, yellow, or green. However, checking the diamond fluorescence is not included in the diamond grading process.

What Does Fluorescence Mean?

The term “fluorescence” is used to pertain to the natural optical phenomenon where an object or substance emits a visible glow when exposed to light — UV rays, direct sunlight, and indoor lighting fixtures. The visible light produced by the object is due to the electrons present in atoms and molecules. When exposed to light, electrons get excited and jump to a higher energy level then return to their original state. The light you see is the excess energy from the electrons.

The diamond fluorescence colors the object produces differ depending on the properties of the diamond.

What Causes Fluorescence in Diamonds?

Fluorescence in diamonds is usually caused by the presence of nitrogen atoms within the diamond’s structure. When it is exposed to UV light, these impurities absorb the energy and emit a visible glow due to the excess energy. Most of the time, you’ll see blue fluorescence in diamonds but in some cases, there are light yellow or green glows as well.

How is Diamond Fluorescence Measured?

The diamond fluorescence is measured using a grading scale where the color, intensity, and laboratory grading report are considered. When a diamond is checked by an expert jewelry appraisal, they’ll check the color and intensity of the fluorescence. The intensity uses the terms None, Faint, Medium, Strong, and Very Strong to identify the level of diamond fluorescence when it is exposed to UV light.

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How It Affects Diamond Quality and Value

The fluorescent diamonds have different effects on its value and quality depending on their intensity. Faint to Medium fluorescence has little to no negative impact on both the quality and value of the precious gemstones. However, for Strong to Very Strong fluorescence in diamonds, it’s another story. 

Strong and Very Strong fluorescence-grade diamonds have a hazy or milky appearance when exposed to UV light which can reduce the perceived quality of diamonds and, hence, its value. The milky appearance and haziness make the diamonds look less transparent and brilliant.

Is Diamond Fluorescence Good or Bad?

Whether diamond fluorescence is good or bad depends on personal preference and the characteristics of the white diamonds. For example, some people appreciate the unique characteristics the fluorescence of diamonds add to the precious gemstones. Also, blue fluorescence in diamonds makes yellow diamonds look whiter. However, a strong blue fluorescence diamond might appear hazy which some people are not fond of. 

Factors Influencing Fluorescence in Diamonds

The diamond fluorescence is affected by natural and structural factors. Here are the factors that influence the presence, intensity, and characteristics of fluorescence in colorless diamonds.

Intensity and Color of UV Light

The color of the UV light sources will affect how the diamond fluorescence’s color appears. Also, the strength and length of UV light exposure influence the diamond fluorescence visibility. In some instances, the fluorescence will look more visible under an intense UV light source.

Presence of Nitrogen and Their Aggregates

The presence of nitrogen is the main cause of fluorescence in diamonds. The higher the nitrogen content of the diamonds is, the higher the possibility of having diamond fluorescence when exposed to UV light. Also, the nitrogen atom arrangements and their aggregates influence the intensity and color of the fluorescence.

Diamond Color and Cut

Diamonds that are precisely and expertly cut will show different fluorescence diamonds than less precisely cut options. While the diamond’s color grade can affect how the fluorescence is perceived. 

Natural Variability

Natural variability is important for both diamond grading services and fluorescence. This includes the diamonds’ chemical composition, earth conditions where they’re sourced, and the formation history.

Exploring the Different Diamond Fluorescence Levels

To come up with a level of fluorescence, the color and intensity of the fluorescence in diamonds are considered. There are 5 levels or grades used for diamond fluorescence, namely: 


As the name suggests, None Fluorescence means there’s no visible glow when the diamond is exposed to a UV light source. Also, the diamond doesn’t glow in any color.


Faint Fluorescence indicates there’s minimal visible glow when the diamond is exposed to a UV light source. The visible is weak and might not affect the appearance of the diamond.


When the diamond is exposed to UV light and has a moderate level visible glow, it’s graded as Medium fluorescence. The diamond with fluorescence is subtle but more noticeable than Faint Fluorescence.


Diamonds with a more obvious visible glow when exposed to UV light are labeled as Strong Fluorescence. The diamond fluorescence can easily be observed but its appearance might look hazy or milky.

Very Strong

Very Strong Fluorescence is given to diamonds with an intense visible glow when exposed to UV light. The appearance of diamonds with Very Strong Fluorescence will make them look hazy and milky which some people don’t fancy.

Do Fluorescent Diamonds Matter in Jewelry Appraisal?

The diamond fluorescence will have minimal to no effect on the diamond prices and values. When an experienced jewelry appraiser grades and appraises precious gemstones like diamonds, the 4Cs are used — carat weight, cut, color, and clarity. This doesn’t include the fluorescence in diamonds. They look at the whole picture and consider all relevant factors which affect the diamonds’ value. 

Again, the diamond fluorescence level depends on personal preferences and priorities other than the diamonds’ value.

Get the Right Diamond Appraisal at Willyn Villarica Jewelry

Determining the diamond fluorescence level is not an easy task. It takes years of experience, knowledge, skills, and expertise to be able to identify the right diamond fluorescence. If you have diamonds and want them appraised and find out their fluorescence level by expert jewelry appraisals, book an appointment with Willyn Villarica Jewelry.

Willyn Villarica is your trusted partner for jewelry appraisal services, catering to clients around the globe. Our expertise and commitment to excellence ensure accurate and reliable assessments of your precious gemstones. It’s important to note that while we offer our services worldwide, clients are responsible for covering all travel expenses. Don’t miss out on the opportunity to have your diamonds expertly graded by Willyn Villarica. For inquiries or appointments, reach out to us via email at admin@willynvillaricajewelry.com, or engage with us on our official Facebook (Willyn Villarica Jewelry) and Instagram (@willynvillarica_jewelry) accounts. Furthermore, we are readily available for direct communication at +63279497547.

  • Willyn Villarica

    Willyn Villarica, a third-generation jeweler from the Philippines, brings a wealth of expertise to the world of gemology and jewelry appraisal. As a licensed Graduate Gemologist, accredited by the prestigious Gemological Institute of America, she is not only a master of her craft but also holds the distinction of being the first Filipino member of the National Associ...

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